Twin-clutch, twin-shaft, dual shaft, or dual clutch transmissions of the alternating shifting type are well known in the prior art. Various types of twin clutch transmissions have been proposed and put into practical use, particularly in the field of wheeled motor vehicles. Traditional twin clutch transmissions are of a type in which gears are parted into two groups, each group having an individual main clutch, so that the operative condition of each group of gears is carried out by selectively engaging a corresponding main clutch. Twin clutch transmissions are used in vehicles to improve the transition from one gear ratio to another and, in doing so, improve the efficiency of the transmission. The gears of each group are typically individually engaged so as to rotatably connect a transmission input shaft to a transmission output shaft for transmitting torque at differing ratios. The differing ratios may be engaged by multiple shift clutches.
A typical dual clutch is illustrated in commonly owned U.S. Pat. No. 7,082,850, to Hughes, the disclosure of which is hereby incorporated by reference in its entirety. Many main clutches for dual clutch transmissions include clutch packs, having a plurality of clutch disks, for engaging and disengaging each gear group with the engine. In some applications, the clutches are actuated by hydraulic pistons for engaging and disengaging each clutch pack. Typically, the clutch packs are located radially outside of the hydraulic pistons to prevent fluids that are heated by the clutch packs from contacting the outer surfaces and seals of the piston assemblies.